Re: File Transfer Problem (IIgs)

[mjmahon@aol.com (Michael J. Mahon)]

Iosaef the Irascable asked:

<snip>
>    The problem is that when I try to Unshrink a file directly off of CD 
>(GSHK 1.1), most of the time, it'll bring up numerous CRC errors, and 
>occasionally a fatal (to the decompression) error.  Now, copying those 
>files to the HDD -partially- solves that problem.  However, it doesn't 
>always...
>
>     What makes the problem a mentionable one on here, is that identical 
>files (from earlier CD backups, from the HFS partition, from a ProDOS or 
>HFS formatted Zip Disk, from a serial-transferred version, or from a 
>pre-existing SHK on my HDD), will sometimes exhibit this behavior, 
>sometimes not.  Sometimes, all I have to do is re-unShrink the SAME FILE 
>(even off of CD!) to get a successful decompression.

This indicates that the problem is an intermittent or transient error.
It is most likely occuring during the data transfer from the SCSI
devices (particularly the CD drive) to the Apple.

One possible cause is electrical noise caused by the CD drive
during the transfer (or even during the decompression).

One way to isolate the problem a bit is to copy the shrunk file
from the CD drive to the RAM drive, then uncompress from the
RAM drive to the RAM drive.  Since the SCSI bus will be idle
during the decompression, it should work or not work completly
repeatably.  (If it is still not repeatable, then I would suspect a
memory problem, possibly induced by a marginal power supply.)

If the problem is data corruption while reading from the CD drive,
it may be caused by improper SCSI bus termination, including
termination power.

A SCSI bus with more than one device should be terminated
at each end, and one device should supply termination power.
Any deviation from this scheme will result in improper or
unreliable operation.

If the termination is proper, but intermittent errors still occur,
you may have a bad connector or cable, or a bad device.
Swapping cables may fix the problem, or move it to another
device.  You can also try removing unused devices to see if the
problem changes.

-michael

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